The interaction of metastable helium atoms with alkali atoms

Abstract

Using crossed beams of ground state alkali atoms A (A = Li, Na, K, Rb, Cs) and metastable He(23 S), He(21 S) atoms, we have measured the energy spectra of electrons resulting in the respective Penning ionization processes at: thermal collision energies. The data are interpreted to yield the well depthD * of the2Σ interaction potentials as follows: He(23 S)+A:D * (A=Li)=868(20) meV;D * (Na)=740(25) meV;D * (K)=591(24) meV;D * (Rb)=546(18) meV;D * (Cs)=533(18) meV. He(21 S)+A:D * (Li)=330(17) meV;D * (Na)=277(24) meV;D * (K)=202(23) meV;D * (Rb)=219(18) meV;D * (Cs)=277(18) meV. The well depth for He(23 S)+A(2Σ) is always close to 80% of the well depth for Li(2s)+A(X 1Σ). The ionization cross sections for He(21 S)+A are about 3 to 4 times larger than those for He(23 S)+A.